A known map matching technology is adopted in an on-vehicle navigation system when indicating the subject vehicle position on a roadmap so as to ensure that the subject vehicle indicated on display never erroneously assumes an off road position by correcting the subject vehicle position detection results provided by a GPS, a gyro and the like in correspondence to the road layout. However, over an area such as an area around a branching point, where a plurality of roads are present in close proximity to one another, it may not always be possible to accurately determine to which road the subject vehicle position detection results should be corrected in conjunction with this map matching technology. Under such circumstances, the subject vehicle may be initially indicated on a road on which it is not traveling and then the subject vehicle position may be abruptly switched onto the road on which it is actually traveling. This phenomenon is referred to as position jump.
There is a navigation system known in the related art that has a function (auto-reroute function) of automatically searching for a new recommended route relative to the current subject vehicle position if the subject vehicle position moves out of the initial recommended route. If the position jump phenomenon described above occurs while the subject vehicle is traveling on the recommended route, causing the subject vehicle position to be briefly indicated to be off the recommended route and then be indicated on the recommended route again, an auto-reroute will be executed at each of the subject vehicle positions indicated on the map in the navigation system. The user will find this redundant execution of auto-reroute distracting and confusing. A route guiding apparatus in the known art (see patent reference literature 1) prevents such redundant auto-reroute execution by disallowing the auto-reroute in situations in which the position jump phenomenon is likely to occur.
Patent reference literature 1: Japanese Laid Open Patent Publication No. 2000-241182
The route guiding apparatus disclosed in patent reference literature 1 disallows the auto-reroute when there is a plurality of map matching candidate roads, e.g., when the subject vehicle is traveling in an area around a branching point. As a result, even if the current vehicle position is briefly indicated to be off the recommended route due to the position jump phenomenon, the auto-reroute is not executed.